1. Field of the Invention (Technical Field)
The present invention relates generally to the field of multiple imaging systems, more specifically to methods and apparatuses for causing a single imaging lens system to simultaneously form multiple images on multiple imaging sensor planes. The images are preferably substantially identical except for different light levels so that the multiple images are of sufficient quality and similarity that they may be compared and/or combined (typically pixel-by-pixel) to create a single instantaneous high dynamic range (HDR) image. Alternatively, the images are substantially identical except for different focuses or different magnifications.
2. Description of Related Art
Note that the following discussion refers to a number of publications and references. Discussion of such publications herein is given for more complete background of the scientific principles and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
In recent years, the goal of producing high dynamic range (HDR) images has been approached from many different directions. U.S. Pat. Nos. 7,084,905 and 7,397,509 and U.S. Pat. Appl. Ser. Nos. 2005/0099504 and 2008/0112651 each describe an apparatus and/or method for producing HDR images using specialized sensor arrays with novel pixel properties. U.S. Appl. No. 2008/0055683 describes a system and method for synthesizing an HDR image using a single optical image. U.S. Pat. No. 5,801,773 and U.S. Pat. Appl. Ser. Nos. 2005/0041113, 2006/0209204, 2007/0025717, and 2008/0094486 each describe an apparatus and/or method for synthesizing HDR images from sequences of images taken at different moments in time. None of these patents describe a method for optically producing multiple images on multiple sensor arrays simultaneously.
Devices and methods for optically producing multiple simultaneous images have been known for over 100 years. U.S. Pat. No. 347,451 describes an apparatus for using multiple imaging lenses to create simultaneous images on a single image plane. U.S. Pat. Nos. 3,601,480, 5,153,621, 5,194,959, 5,734,507, 5,835,278, and 5,926,283, European Pat. Appl. No. 91118422.4 (Publication number 0 484 802 A2), Japanese Patent Publication No. 60-213178, and Aggarwal & Ahuja, Split Aperture Imaging for High Dynamic Range, International Journal of Computer Vision 58(1), 7-17 (2004) each describe a method and/or apparatus for splitting an image-forming beam into spatially-distinct sections using a pyramid-shaped mirror or other total reflective device. U.S. Pat. Nos. 5,024,530, 5,642,191, 6,856,466, and 7,177,085 each describe a method and/or apparatus for splitting an image-forming beam into spatially-distinct sections using a prism or other refractive device. All of these papers and patents describe methods and/or apparatuses that suffer from parallax error, due to the fact that the image-forming beam in each case is split into subsections that are spatially distinct from one another at the point of splitting. None of these patents or papers describe or suggest a method for splitting an image-forming beam using a partially-reflecting beamsplitting device that provides light for each split portion from the entire original image-forming beam.
The use of prisms and/or beamsplitters to form a plurality of subimages having different color or polarization characteristics has been studied and explained in great depth. U.S. Pat. Nos. 2,560,351, 2,642,487, 2,971,051, 3,202,039, 3,381,084, 3,653,748, 3,659,918, 3,668,304, 3,802,763, 3,945,034, 4,009,941, 4,268,119, 4,933,751, 5,134,468, and 7,283,307 each describe a method and/or apparatus that explicitly splits the image-forming beam into separate subimages on the basis of color (using explicitly dichroic and/or color-separating means). None of these patents describe a method for splitting an image-forming beam into subimages that have identical color and/or wavelength properties. Furthermore, U.S. Pat. Nos. 3,202,039, 3,659,918, 3,802,763, 4,009,941, 4,084,180, 4,268,119, 5,134,468, and 6,215,597 each describe a method and/or apparatus that relies on passing the image-forming beam through solid glass prisms that have tilted glass faces in contact with air: a situation that immediately precludes their use for producing multiple high-resolution sub-images with identical color and/or wavelength properties.